Protective layer on photographic films



April 18, 1933 M. HAGEDO'RN 1,904,221

PROTECTIVE LAYER ON PHOTQGRAPHIC FILMS Filed April 25. 1927 Senslizlzed fmulszbn V7 I A v Film body of a cellulose derivative Profecfive layer comprising a pel/z'c/e 0 an eszerqerivafz've of cellu lose conzaamhg several dzfierenf radic es 0.: subshiuzms Jul/6712 07 Patented Apr. 18, 1933 UNITED STATES PATENT OFFICE MAX HAGEDORN, F DESSLU IN ANHALT, GERMANY, ASSIGNOR, BY MESNE ASSIGN- MEETS, TO .AGFA ANSCO CORPORATION, OF

TION OF NEW YORK BINGEAMTON, NEW YORK, A CORI 'ORA- PROTECTIVE LAYER ON PHOTOGRAPHIG FILMS Application filed April 25, 1927, Serial Ho..-188,567, and in Germany May 1, 1926.

One applies a protective la er to the back surface of a photographic v lm for several purposes; for instance for preventing the film from rolling up during development, fiiring and drying, for making the film less liable to damage, making it softer and better adapted to slide, which is of particular importance in the cinematograph film; for protecting the film against electric discharges which are liable to occur owing to the electrical excitation of the film, it may be by movements in the cinematograph apparatus, for minimizing the alteration in length and breadth of the film owing to the eflect of atmospheric moisture.

For these purposes protective layers of various kinds have been suggested, for example varnishes, resins, gelatin, individual cellulose esters and ethers, either alone or with addition of electrolytes, substances which are hygroscopic or diminish the surface tension or friction of the film. Another proposition has been that the back surface of the emulsion carrier should be varied in its composition by treating it with solvents, with or without the addition of electrolytes or substances which are hygroscopic or diminish the surface tension or the friction of the surface.-

In order to lend to the protective layer the properties desired for the particular purposes, the layer has been made up of advantageously mixed substances which are more or less foreign to the emulsion carrier.

As contrasted with this practice a protective layer which does not consist of a IIllX- ture but is a chemical-individual compound of the properties required for the purpose would be a technical advance.

The present invention consists of a protective layer made of cellulose derivatives other than nitroacetate soluble in organic solvents and containing several different radicles as substituents, particularl radicles of more than one acid or esides other groups radicles of acids. Such compounds maybe obtained from cellulose derivates having still esterifiable hydroxyl groups, particularly from mono-esters, diesters, mono-ethers, di-ethers or mixtures of ample, if a film having a high capacity for sliding and small shrinkage is required there may be used cellulose-acetate-stearate as protective layer. The same effect has a protective layer made from cellulose-ethyl-etherstearate. When protection against electric discharges is in question the layer may consist of cellulose-ether-phosphate or celluloseacetate-phosphate;

In carrying out the invention a solution of the said cellulose derivates containing several different radicles as substituents is applied to the photographic film, particularly to the back surface of such a film.

The following examples illustrate the. invention without limiting it:

Ewamgvle 1.60 grams of cellulose-acetatephosphate are dissolved in 3750 cc. of acetone and 1600 cc. of water, with addition of 300 cc. of glycol mono methyl ether acetate. The layer produced by applying this solution in the known manner to the back surface of the film imparts good protection against electric discharge.

Example 2.-For producing a protective layer on the back surface of the film there is used a 1 per cent solution of cellulose-ethylether-stearate or cellulose-acetate-stearate in a mixture of 1 part of alcohol, 3 parts of henzene and 2 parts of acetone. This layer greatly diminishes the resistance of the film to sliding in the cinematograph apparatus.

The aforesaid solutions may contain still other additions remaining in the dry layer.

The accompanying drawing shows on an enlarged scale in section a film provided with a protective layer according to the present go, I mower invention. It is to be unaerstood thee the invention is not limite to films embodl 1- the especial ratio of thicknesses of layers represented in this drawing.

5 Having now periieulerly described and aseerse-ined the nature of my sew invention and in What manner the some is to be performed, I declare that what I claim is l. A photo rephic film with e protective N layer on its iack surface, sairi layer comprising e compoun& of the group consissing of? ceiiuiose-ether-sigeerete, cellulose-etherphesphete, cellulose eceiete steerete, end cellulose-acetate-phosphate.

15 2. A photographic film with a protective iey er on its back surface, seidi layer consisfiing of cellulose ether-phosphate.

, 3. A photographic with a protective Beyer on its beck surfece, said! layer comprism ing s ceiiulose derivative of the group (203' sisting of eeiiuiose mixed esters of two faity eeiais, cellulose mixeoi esters of one fetiy acid and phosphoric acid, eeiiulose ether esters of fetty eoids, em? cellulose ether esfivers ofi 25 phosphoric eeidl. I

in testimony whereof I efix my signature,

MAX HAGEDQBH. I 

